Vehicle manufacturers continually invest in research and development efforts aimed at improving the fuel efficiency of road vehicles. This is particularly important in the road haulage industry where fuel represents a significant percentage of HGV operating costs. Fuel efficiency is dependent on numerous different factors other than the inherent efficiency of engines. For example, aerodynamic styling features such as cab roof deflectors, air dams, side skirts etc. help to reduce aerodynamic drag with consequent improvements to overall fuel efficiency.
Another key aspect of the fuel efficiency of a vehicle stems from the rolling resistance of its tyres as exemplified in FIG. 1. Different tyre characteristics can influence their rolling resistance to varying degrees such as tread thickness, tyre width, polymer composition, tyre temperature, and tyre pressures. Of these, only the latter is under the direct control of a vehicle driver at any given time.
Tyre inflation systems which employ so called “self-inflating” tyres are known. Such systems allow the adjustment of air pressure within each tyre to be matched with external conditions to thereby improve performance and/or tyre tread life and/or maneuverability on different road surface types.
For example, the Spicer® Tire Pressure Control System (TPCS) by Dana Commercial Vehicle Driveline Technologies provides a driver with six pre-defined pressure settings which can be selected depending upon ground terrain and vehicle load. An alternative solution is the SYEGON® Central Tire Inflation System (CTIS) by Nexter Mechanics. It provides for automatic adjustment of tyre pressure dependent upon vehicle speed, vehicle load (three discrete levels) and terrain type (four types). The Spicer® and SYEGON® systems share a military heritage and are high-cost options which provide only a limited number of pre-set pressure adjustments.
It is an aim of the present disclosure to overcome, or at least ameliorate, one or more disadvantages associated with the prior art.